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DR. SANJAY GUPTA, HOST: Hello and thanks for being with us.

As you may know, I spent the past week immersed in what might be the most upsetting story I think I've ever reported.

I want to start by saying, the kind of horrible violence that we saw in Newtown, Connecticut, it isn't new. In fact, the worst school attack ever took place more than 80 years ago in Bath, Michigan. There was a consolidated school, the pride and joy of that community. But it also meant increased property taxes, and this farmer named Andrew Kehoe, he became angry about that. So get this -- for weeks, he put dynamite under the local school and then eventually blew it up, 38 children died. And then Kehoe killed himself with another load of dynamite.

Now, you know, we'll never truly know for sure why he did all that or what made the young man in Newtown unload a rifle into a classroom full of first graders. But I've looked at other school shootings and they just might provide some clues.

(BEGIN VIDEOTAPE)

GUPTA (voice-over): The first thing you notice when you look around Newtown, everyone has that questioning look, why? What did we miss, if anything? No answers yet, just hindsight.

(on camera): To try and make some sense of the tragedy here in Newtown, Connecticut, medical investigators often look for evidence of patterns, not talking about looking at clothing styles or musical preferences or even lifestyle, but rather looking for evidence of specific plans, could get some clue as to what was happening in the person's mind and in their brain.

(voice-over): It's hard to know because thankfully there are relatively few tragedies like this one, but a close look at 10 of the most analyzed mass murder cases in history provide some remarkable insight.

According to this research published in the journal "Aggression and Violent Behavior," doctors typically start by placing these killers into three categories, traumatized, psychotic, and psychopathic.

In 2005, a 16-year-old killed nine people at a school in Minnesota. A look into his past revealed an abused boy with an awful family history. The shooter had been previously traumatized. The Virginia Tech shooter killed 32 people, six were murdered in Arizona and 12 lives were taken in an Aurora, Colorado movie theater. In each case, the killers showed signs of psychotic behavior, severe delusions and paranoia.

Thirteen people were shot and killed in Columbine, Colorado. One of the murderers was later discovered to be a textbook psychopath and we now know he even laughed while gunning down his victims. Looking back, none of them had snapped. They had all left clues, pieced together after it was too late.

(on camera): We still don't know much about the shooter who lived in this home, but there is something else to consider -- what medications, if any, he was on, and specifically I'm talking about antidepressants.

If you look at the studies on other shootings like this that have happened, medications like this were a common factor. Now, I want to be clear, I'm not saying that antidepressants can't be effective, but people seem to agree there is a vulnerable time when someone starts these medications and when someone stops could lead to increased impulsivity, decreased judgment, and making someone out of touch.

(voice-over): None of this is an excuse and it's never one thing. None of these behaviors will fully predict or explain why, but soon again there will be hindsight that might just help prevent another tragedy.

(END VIDEOTAPE)

GUPTA: Now, in terms of medication, one report showed over a seven- year period, there were 11,000 episodes of violence related to drug side effects. But it is worth noting that if a death was involved in that violence, most often it was a suicide. An individual did not, in fact, harm others. You know, a lot to talk about.

I want to bring in Dr. __ from Harvard Medical School. He's an expert in forensic psychiatry. He's also the author of this book, "Almost a Psychopath."

Thanks for joining us.

I'm sure you've been thinking about this a lot. Lots of questions. You've studied rampage killers. And you agree that there isn't just one type, but these shooters fall into, but I guess the question is, are they by definition mentally ill, just given what they -- the crime they just committed?

DR. RONALD SCHOUTEN, DIRECTOR OF LAW & PSYCHIATRIC SERVICE, MASS. GENERAL HOSPITAL: Well, thanks for having me on, Sanjay. And it's as complicated a picture as you lay out here. As you point out, there are these different categories of people who engage in these acts of violence. So, most of whom do not have a serious mental illness. And we know that the vast majority of violent crimes and acts of violence in this country are not committed by people with mental illness. However, there is a small group of people who are predisposed, in connection with mental illness, who have complicating factors of substance abuse and other dispositional risk factors.

GUPTA: And just by saying they don't have mental illness, does that mean they weren't diagnosed, they weren't treated? How do you -- I mean, do we know for sure they didn't have it?

SCHOUTEN: Well, we don't know for sure. But in general when we look at many of these cases, especially for example school shootings and workplace violence -- episodes of workplace violence, we see people who don't have what we consider a severe mental illness such as schizophrenia, bipolar disorder, major depression. They have characterologically, a personality disturbances, certainly, and severe personal traits, along the antisocial realm. That's when we get into the issue of psychopathy.

And certainly, you can psychopathic traits, combined with someone who has a significant illness. But the majority of the cases, there is not a diagnosable severe mental illness.

GUPTA: Yes. I mean, there is no hard and fast rules here. That's what I keep hearing. I mean, I'm sure, you know, everyone has been following this story of Newtown so closely. What occurred to you when you heard this?

SCHOUTEN: How much more we need to know. How much more we need to know about this individual. You know, we all like to search for so much simple solutions and put people into categories and put these situations in categories because it gives us at least an illusion of some sense of control. I'd like to know a lot more about him in terms of his personality, about his criminal history, about his diagnosis, about his relationships. When we -- when we think about risk and violence, we think about three sets of factors, individual risk factors, environmental risk factors and situational triggers.

And one of the things that we've heard about in this case about is the possibility that his mother was about to commit him to the hospital. And I've had a number of cases in which people who were paranoid for many years suddenly turn on the family member, often their mother, because they believe the mother has now gone over to the other side and has joined the conspiracy against them.

GUPTA: You know, it's -- I made the point earlier, it's -- I'm not sure any answer will prove satisfactory here, a lot of people speculating, as you say. But I really appreciate your insights, to the extent people who suffer with mental illness, again, not saying he necessarily had it. But we don't want people to be stigmatized and we want to make sure factual information is getting out there.

So, I really appreciate it.

SCHOUTEN: Absolutely. Thank you.

GUPTA: And so many parents will be watching this week and thinking, could that be my kid? What happened to this shooter? And how would you know? What could you do about it? We're going to continue that part of the discussion, next.

(COMMERCIAL BREAK)

GUPTA: There's been a lot of attention put on the mother of the young man in Newtown. Was she wrong to keep all those guns, for example? Did she know her son was a potential killer?

And what we know for sure is parenting a troubled child, especially as they get older, can be a tremendous challenge.

Andrew Solomon is the author of "Far From the Tree: Parents, Children and the Search for Identity." And he joins us to talk about this.

You know, thanks for joining us I'm been watching your comments on this, I can your voice is really important, around this issue. You know, one thing I should point out and you know this already -- we don't know if Adam Lanza, the Connecticut shooter, had mental illness, although some family friends out there say he did.

Dr. Schouten, who just joined us, said he thinks most of people who commit these mass attacks are not mentally ill.

I just wondered, Andrew, what do you think of that?

ANDREW SOLOMON, AUTHOR, "FAR FROM THE THREE": Well, first of all, it's a pleasure to be on the show. And I think it's a semantic argument. I think people who are mentally solid and sane don't go and shoot up a whole room of first graders.

There is always the danger that by suggesting that people who do these things have mental illnesses, we somehow implicate many other people who have mental illnesses and will never do any such thing. And there is no particular likelihood of people with mental illnesses as committing crimes like this.

But I think the fact of the crime itself shows that there is some kind of profound dysfunction and I think psychopathy, even though it's not listed in the diagnostic and statistical manual, along with schizophrenia and so on, is equally a mental illness.

GUPTA: Yes, I heard a stat that people with many mental illnesses are more likely to be victims of violence as opposed to perpetrating it. So, I think -- again, I think your point is a good one. In the book, which is a terrific book, I mean, you write about the families of people who develop schizophrenia, and we've been hearing a lot about how hard it is to push your child into treatment.

I'm just curious. You know, as part of the research for your book, was that the case with the people you met and interviewed?

SOLOMON: You know, schizophrenia is a very disturbing illness for many, many reasons. But one of them is that it has a relatively late onset stage. It tends to come on in late adolescence or early adulthood. It's very difficult when you see someone whom you've known well and loved and admired for 20 years turn into somebody else, to figure out what to do about it. And we tend to stick with a kind of bacterial model in which we think there is something that has happened to this person, and if we took it away, the person would be there whole and intact underneath it.

And, in fact, schizophrenia can, in many cases, obliterate much of the person who was there.

Now, there are people who respond incredibly well to the medications and treatments that there are for schizophrenia. There are people who have the discipline to pursue them. And there are many people with schizophrenia leading rich and rewarding and productive lives.

But it's a difficult illness to manage. And when it comes on, it's shocking. It's shocking how profoundly it changes people and it's shocking how the command hallucinations they have, the sense of voices instructing them to do things they would never do can determine their behavior.

GUPTA: So, what do you do? I mean, right? I mean, I think people watching, Andrew, are thinking, OK, gosh. I mean, what does this all mean?

If -- if I'm worried about my own child, or -- I mean, you wrote about how people became afraid of their children. What do you think is the message for parents, perhaps, of people just post-adolescence who were watching this and are concerned?

SOLOMON: I think the biggest message is vigilance. I think children should be screened more often than they mostly are. I think parents who think their child's behavior is strange should get that child in to see a psychiatrist.

I think if you remove some of the stigma, we'll make it easier for people to talk about their hallucinations or anything else that they're going through that is distorting their sense of reality. But I think it's really -- I mean, the question ultimately is attention. And the attention has to come from the parents, the attention should come from the schools, the attention should come from the society at large. And when it becomes clear that it's needed, the attention should come from medical professionals.

GUPTA: As I said, Andrew, it's always a pleasure to speak with you. I enjoy hearing your comments. Thanks for joining us.

SOLOMON: It's a pleasure to be here. Thank you.

GUPTA: And turning back to the victims now. You know, for most of us, it's almost inconceivable what those children in Newtown experienced and what the survivors are still going through now.

But this week my friend and colleague, Elizabeth Cohen, met two young men who have been there before and want to share their stories in the hopes they can help.

UNIDENTIFIED FEMALE: She walked past the body. She saw the principal. She saw the blood.

COHEN: Physically, they escaped, but how will these young survivors do mentally?

UNIDENTIFIED MALE: A very serious situation at the North Valley Jewish Community Center --

COHEN: Ben Kadish and Josh Stepakoff know what it's like to face the nightmare.

Thirteen years ago, the boys were at summer camp in Los Angeles when a gunman stormed in and shot them. Ben was 5.

What do you remember happening around you?

BEN KADISH, SURVIVED MASS SHOOTING AT AGE OF FIVE: Screaming, tons of screaming.

COHEN: Josh was 6.

JOSH STEPAKOFF, SURVIVED MASS SHOOTING AT AGE OF SIX: He came in and he shot all the way around and the next thing I remember I was just getting up and running as fast as I could that way.

COHEN: The boys survived, but were never the same emotionally.

STEPAKOFF: I didn't live a normal childhood. In no means did I have a normal childhood.

COHEN: The shooter, Buford Furrow, had robbed them of their security.

When you were dropped off at school, you wondered am I safe?

KADISH: Yes.

COHEN: For how long?

KADISH: Probably through middle school.

STEPAKOFF: If we heard helicopters, sirens, loud noises, anything that would startle me, the house was on lockdown.

COHEN: So you would go around and lock doors? STEPAKOFF: I locked every door. I locked every window.

COHEN: Why did you lock every door and window?

STEPAKOFF: That was the closest thing I could feel to safe.

COHEN: Now 19, these two young men are among the few people who've experienced what the Connecticut children have experienced.

STEPAKOFF: The pictures of the kids being taken out and standing in this line, I could accidentally mistake the pictures from when I got shot.

COHEN: They worry for the Newtown children.

KADISH: I think they're going to feel, you know, afraid of the dark, afraid of loud noises.

COHEN: What advice would you give to these parents in Connecticut?

STEPAKOFF: Listen to your kids, you know? They're a lot smarter than we take them for and, so, you really have to just listen to them and be understanding to them and know that there will be times when they really do want to talk about it and there will be times when they don't.

And if they don't want to talk about it, don't push them.

(END VIDEOTAPE)

GUPTA: Elizabeth Cohen joins us now.

You know, I'm always struck how mature kids become after this.

COHEN: They have lots of words of wisdom and I wonder if they'll fly across the country and get to meet those kids. I asked Ben Kadish, what was the one thing your parents did most helpful? And they would say to him, Ben, you are stronger because of this.

So he would repeat kind of this -- he called it a slogan. Ben Kadish can do anything. Because he said if I survived that, I can do anything.

GUPTA: Yes. And are they still fearful? He was talking about, you know, how it was in the immediate aftermath. They're grown up now. Do they still seem fearful at all?

COHEN: They do. They will say that themselves. You know, when they were thinking about where to go to college, they're both 19. They thought about going out of state but they decided to stay right in Los Angeles because they said they have moments that are tough.

And when they have a tough moment, they want to be a five-minute drive home. They don't want to have to be a plane ride home. That's their safety zone. GUPTA: It's interesting. I'm sure you thought about this as well with your kids. People most exposed, like the two men in the piece, they obviously -- they were injured are the most at risk. But then people who witness it, people who are close by it. But then there is a whole bunch of kids all over the world or farther away.

How much of an impact do you think it makes on your kids and my kids?

COHEN: I think that we're fortunate in that we can limit it as much as we possibly can. You know, I've made a point of not emphasizing it with my children. Not talking about it too much this past week. And we kept the television off. If they ask about it, we answer their questions.

But I think one of the keys is, is to just sort of keep it away from them, if you can.

GUPTA: Right. Yes. I've tried to do that, as well. But it's just social media nowadays, amazing the questions they ask.

Good stuff. Thanks, Elizabeth.

COHEN: Thanks.

GUPTA: And there's another thing that caught my eye as well up in Newtown. You may have seen some of these images. The comfort dogs -- nine specially trained golden retrievers made their way up from Illinois to Connecticut to help children and adults alike cope and grieve. You know, these pooches, I've seen them in other places, they've been to flood zones, hurricane zones and now Newtown, hopefully bringing some smiles and sense of relief to a community that's still trying to make sense of what has happened here.

Up next, another type of assistance dog -- in this case, to alert a young boy and his parents to impending seizures. You're going to meet 9-year-old Evan Moss and his dog, Mindy.

(COMMERCIAL BREAK)

GUPTA: Welcome back to SGMD.

You know, I want to take a moment now to share a nice, uplifting story with you. It's about a boy, his dog, and the spirit of giving.

(BEGIN VIDEOTAPE)

GUPTA (voice-over): Nine-year-old Evan Moss is a boy who seemingly only cares about one simple thing. Unfortunately, Evan's life was not so simple.

LISA MOSS, EVAN'S MOTHER: When Evan was a couple weeks old, he started having these little shaky movements. It was one arm that would switch a little bit and last a few seconds.

GUPTA: Robert and Lisa took their son to dozens of doctor's appointments. And Evan was eventually diagnosed with tuberous sclerosis complex. It's a rare genetic disease that causes non- malignant tumors to grow inside the brain and in other vital organs.

Evan's TSC includes one of the hall mark symptoms, potentially life- threatening seizures that can happen at any moment.

Since Evan's parents cannot watch over him all the time. They began to look for an extra set of eyes, ears and a nose.

ROBERT MOSS, EVAN'S FATHER: We were also finding out that not only did these dogs respond to seizures, that they have the capability to alert you, to tell you that the individual might have a seizure or might soon be having a seizure.

GUPTA: As you might imagine, these types of highly trained service dogs that can literally sniff out chemical changes in the body leading up to a seizure don't come cheap.

LISA MOSS: A service dog costs anywhere $22,000 to $25,000, and they ask for each recipient family to fundraise $13,000 of that to offset the cost. And as part of the application, they ask for something from the child receiving the dog. He said, can I write a book?

EVAN MOSS, SUFFERS FROM EPILEPTIC SEIZURES: "My Seizure Dog" by me. This seizure dog knows when I have a seizure. We will be best friends.

GUPTA: Big sister, Aria, suggested their parents self publish Evan's book on Amazon where it shot to the top of one of the site's bestseller list. A book signing followed at a neighborhood coffee shop. The turnout was overwhelming.

LISA MOSS: We did end up raising around $45,000 and helped about seven additional children complete their fundraising.

GUPTA: Mindy rarely leaves Evan's side during the day, at school, on the bus, in the backyard. Never leaves his sight at night.

EVAN MOSS: The seizure dog will sleep with me. If I have a seizure in my sleep, the seizure dog will tell my parents.

GUPTA: If you want to learn more about seizure assistance dogs, you can buy Evan's book or even make a donation, do it all by logging on to dogforevan.com.

You know, for many people, this is a popular regift. But did you know that the fruit cake may, in fact be the original energy bar. Historians trace its roots back to the middle ages when crusaders carried it up for nourishments on long trips to the Holy Land.

And today, the holiday favorite is finding fans in bikers and hikers are looking for foods that are high in carbohydrates that can fuel them on those long hauls. One serving, in case you're curious, packed with nuts and dried fruit. It can have as much as 11 percent of your daily iron intake. So, maybe it really is the food that keeps on giving.

You know, all those tempting treats, you know what I'm talking about, this type of year can wreak havoc on your body. So, how to chase life to 100 this holiday season. It's my gift to you.

(COMMERCIAL BREAK)

GUPTA: You know, the holidays can be a wintry mix of happiness and stress. But did you know that more people die of heart attacks on Christmas Day than any other day of the year? People are traveling more than usual, they're carrying heavy luggage, walking long distances in airports. There's also the added stress of family, heavy meals and alcohol.

So, obviously, try and keep the stress, the fatty foods and alcohol to a minimum. Also, manage your expectations when it comes to relationships, especially in your family. Ask for help with your luggage.

Pay attention as well to the symptoms of a heart attack. Chest pain, yes. But also shortness of breath, sweating, nausea -- anything that comes on suddenly is unusual.

If you're concerned, go to the hospital. They're going to be working there, whether you come in or not.

That's going to wrap things up for SGMD, but stay connected with me at CNN.com/Sanjay. Let's keep the conversation going on Twitter @DrSanjayGupta.

Time now, though, to get you a check of your top stories in the "CNN NEWSROOM."